1. (Field of the Invention)
The present invention generally relates to an automobile body structure and, more particularly, to a rear bottom frame structure, or a rear underbody structure, for automobiles.
2. (Description of the Prior Art)
Japanese Laid-open Utility Model Publication No. 58-45173, published in 1983, discloses a rear underbody structure for automobile comprising a pair of side sills each having a generally closed cross section and extending in a direction longitudinally of the automobile, said side sills spaced apart from each other in a direction extending widthwise of the automobile, a suspension member connected at opposite ends to the respective side sills and having a generally channel-shaped cross section open towards the front of the automobile, a fuel tank accommodated within the channel-sectioned suspension member, a rear frame connected at a front end with the suspension member, and a suspension arm supported for pivotal movement so as to extend from a portion adjacent the joint between each side sill and the suspension member.
According to the prior art rear underbody structure discussed above, while the rigidity of the suspension member surrounding the fuel tank has been improved, no consideration has been paid to the physical strength and the rigidity of the rear frame during an automobile collision in which the rear frame may be subjected to a considerable impact. In addition, the prior art rear underbody structure cannot exhibit a satisfactory frame rigidity against forces transmitted through the suspension arm longitudinally, widthwise and vertically of the automobile.